Natural killer cells (NK-cells) are a group of spontaneously cytotoxic lymphocytes that destroy tumor cells by lysis with no antigen specificity or restriction by histocompatibility molecules. Monocytes are involved in the regulation of the NK-cell's function, both through mechanisms involving cell contact and through providing soluble NK cell-regulating mediators. Recently, a cell contact-mediated mechanism has been described whereby monocytes regulate NK-cells. This type of monocyte-mediated regulation is exerted by monocytes that are obtained directly from peripheral blood through counterflow centrifugal elutriation (CCE) and is regulated by the biogenic amines histamine and serotonin (Hellstrand and Hermodsson, 1986, J. Immunol. 137, 656-660; Hellstrand and Hermodsson, 1987, J. Immunol. 139, 869-875; Hellstrand and Hermodsson, 1990, Scand. J. Immunol. 31, 631-645; Hellstrand and Hermodsson, 1990, Cell. Imnmunol. 127, 199-214; Hellstrand, Kjellson and Hermodsson, 1991, Cell. Imrnunol., 138, 44-54). These NK-cell regulating mechanisms caused by biogenic amines should be of importance to the NK-cell-mediated defense against metastatic tumors in vivo (Hellstrand, Asea and Hermodsson (1990), J. Immunology 145, 4365-4370).
Interferon-.alpha.(IFN-.alpha.) is an important regulating factor for NK cells. It effectively enhances the NK cell's cytotoxicity (NKCC) both in vivo and in vitro (Trinchieri, 1989, Adv. Immunol. 47,187-376; Einhorn, Blomgren and Strander, 1978, Int. J. Cancer 22, 405-412; Friedman and Vogel, 1984, Adv. Immunol., 34, 97-140).
Owing to the high rate of cancer and the only partially successful treatment methods available today, there is a constant demand for other improved methods of treatment of tumors. There is also a great demand for improved treatment methods for virus infections.